This invention relates to a valve assembly.
A valve assembly typically has a valve obturator e.g. a disc in a butterfly valve, a ball in a ball valve and a tapered plug in a plug valve, supported in a valve body. At one position a drive shaft extends through the valve body and drivably connects the obturator to a valve actuator. Rotation of the shaft by the actuator causes rotation of the obturator through a predetermined angle of e.g. 90.degree. between open and closed positions. In a butterfly valve, the disc may be supported in the valve body at diametrically opposed positions. At one position, the drive shaft extends through the valve body and drivably connects the disc to the valve actuator, while at the other position a stub axle, fixed to the valve body, extends into a socket on the disc. An example of such a butterfly valve is illustrated and described in published European application EP-A-0493921.
In order to determine or monitor the position of the obturator it is known to provide a sensor with an indicator associated with the actuator. However, sometimes, because of wear, damage or other causes the position of the obturator is not accurately sensed or indicated.